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By Rachel Courtland Virgin Galactic’s WhiteKnightTwo is set to take is maiden flight in the next two weeks. The flight will be the first of dozens planned for the high-altitude craft, which could become the first privately owned vehicle to help carry tourists to the edge of space. The high-altitude plane is designed to loft an eight-passenger craft called SpaceShipTwo to an altitude of 15 kilometres. There, the spaceship will detach from WhiteKnightTwo and fire a rocket to take passengers some 100 km above the Earth, where they will experience several minutes of zero gravity (see illustration). The pair are scaled-up versions of a carrier plane and spaceship that won the $10 million Ansari X prize for private spaceflight in 2004. Since WhiteKnightTwo’s unveiling in July, the plane has passed engine and runway tests and taken small hops off the ground. The vehicle, which was developed at Scaled Composites in Mojave, California, is now ready to take off, says Virgin Galactic president Will Whitehorn. “The first flight test will happen very quietly, as these things tend to do, but it will be before Christmas,” Whitehorn told New Scientist. Piloting WhiteKnightTwo may take some finesse. The plane is comparable in size to Boeing’s B-29 Superfortress, a heavy, long-range bomber that flew during World War II. The craft has two fuselages, each with a cabin, that are connected by a 42-metre-long wing capable of holding 17 tonnes of weight. “The configuration makes a lot of sense” for carrying heavy payloads, says MIT aeronautical engineer John Hansman. But as WhiteKnightTwo begins to fly at higher altitudes, pilots might have to watch for effects such as “flutter,” where aerodynamic effects exacerbate natural twisting in the wings. “In very severe cases, you get into an oscillation that actually builds and blows the airplane apart,” Hansman told New Scientist. WhiteKnightTwo might be less susceptible to this effect, since it is made of fairly stiff carbon composite, Hansman says. If WhiteKnightTwo’s test flights go well, the firm plans to begin carrying SpaceShipTwo into the air in mid-2009. In its first solo flights, SpaceShipTwo will gently glide back to Earth without firing its rockets, slowly exploring its ability to reach suborbital space. To ensure safety, WhiteKnightTwo and SpaceShipTwo may require 100 to 200 test flights before the pair are ready to accept passengers, Whitehorn says. This testing regime should still put the firm on track to take its first passengers to the edge of space as early as 2010, Whitehorn says. Virgin Galactic has accumulated some $40 million in deposits from almost 300 interested space farers since the company began selling tickets in 2005. But the firm will have competition in the suborbital space tourism market. On 2 December, XCOR Aerospace announced it would sell rides on its two-seat spacecraft Lynx for less than half of Virgin’s $200,000 ticket. If WhiteKnightTwo’s initial flights go well, the plane will carry atmospheric testing equipment on the rest of its test flights, Whitehorn says. The equipment, part of a collaboration with the US National Oceanic and Atmospheric Administration, will test the air at high altitudes, which are understudied because they are difficult for most aircraft to reach. The data collected could also help calibrate NASA’s Orbiting Carbon Observatory, which will launch in 2009 to measure carbon dioxide levels in Earth’s atmosphere, Whitehorn says. More on these topics: